Processing transdermal alcohol concentration (TAC) data to detect low-level drinking

Subjective intoxication predicts alcohol-related consequences at equivalent alcohol concentrations in young adults using ecological momentary assessment and alcohol sensors

OBJECTIVE

Subjective intoxication (SI) when drinking may serve as an internal barometer of whether to continue drinking or engage in potentially unsafe behavior. Mobile assessments offer the potential to use SI as a prospective risk indicator during drinking episodes; little evidence exists for the validity of real-time SI measures. We test the correspondence of SI with estimated blood alcohol concentration and transdermal alcohol concentration (TAC) in young adults' natural settings. We provide a novel test of whether SI features (peak and mean SI) uniquely predict consequences adjusting for alcohol concentration.

METHOD

Two hundred twenty-two heavy-drinking young adults (Mage = 22.3, 64% female, 79% non-Hispanic White, 84% undergraduates) participated in a 6-day study that used ecological momentary assessment of drinking and TAC sensors. SI was assessed every 30 min during drinking episodes. Multilevel modeling was used to test hypotheses.

RESULTS

Momentary SI and estimated blood alcohol concentration had moderate associations at the moment and day levels (standardized βs = 0.5-0.6); SI was moderately associated with TAC at the day level (βs = 0.5). Associations between SI and alcohol concentration varied widely between persons and across days. Day-level SI features predicted consequences when adjusting for alcohol concentration (incidence rate ratios, IRRs = 1.29-1.70).

CONCLUSIONS

Our two-item SI measure shows evidence of validity in real-world settings with heavy-drinking young adults. SI was significantly correlated with alcohol concentration and was a unique predictor of consequences. The strength of these associations varied greatly across persons and days. Real-time SI measurement may be useful in preventive interventions, but continued research is needed into when and for whom momentary SI is most predictive of risk. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Baseline protective behavioral strategy use predicts more moderate transdermal alcohol concentration dynamics and fewer negative consequences of drinking in young adults' natural settings

OBJECTIVE

Test whether frequent protective behavioral strategies (PBS) users report (a) fewer alcohol-related consequences and (b) less risky alcohol intoxication dynamics (measured via transdermal alcohol concentration [TAC] sensor "features") in daily life.

METHOD

Two hundred twenty-two frequently heavy-drinking young adults (Mage = 22.3 years) wore TAC sensors for 6 consecutive days. TAC features peak (maximum TAC), rise rate (speed of TAC increase), and area under the curve (AUC) were derived for each day. Negative alcohol-related consequences were measured in the morning after each self-reported drinking day. Past-year PBS use was measured at baseline.

RESULTS

Young adults reporting more frequent baseline PBS use showed (a) fewer alcohol-related consequences and (b) lower intoxication dynamics on average (less AUC, lower peaks, and slower rise rates). Limiting/stopping and manner of drinking PBS showed the same pattern of findings as the total score. Serious harm reduction PBS predicted fewer negative alcohol-related consequences, but not TAC features. Multilevel path models showed that TAC features peak and rise rate partially explained associations between PBS (total, limiting/stopping, and manner of drinking) and consequences. Independent contributions of PBS subscales were small and nonsignificant, suggesting that total PBS use was a more important predictor of risk/protection than the specific types of PBS used.

CONCLUSIONS

Young adults using more total PBS may experience fewer alcohol-related consequences during real-world drinking episodes in part through less risky intoxication dynamics (TAC features). Future research measuring PBS at the daily level is needed to formally test TAC features as day-level mechanisms of protection from acute alcohol-related consequences. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Signal processing and machine learning with transdermal alcohol concentration to predict natural environment alcohol consumption

Wrist-worn alcohol biosensors continuously and discreetly record transdermal alcohol concentration (TAC) and may allow alcohol researchers to monitor alcohol consumption in participants' natural environments. However, the field lacks established methods for signal processing and detecting alcohol events using these devices. We developed software that streamlines analysis of raw data (TAC, temperature, and motion) from a wrist-worn alcohol biosensor (BACtrack Skyn) through a signal processing and machine learning pipeline: biologically implausible skin surface temperature readings (< 28°C) were screened for potential device removal and TAC artifacts were corrected, features that describe TAC (e.g., rise duration) were calculated and used to train models (random forest and logistic regression) that predict self-reported alcohol consumption, and model performances were measured and summarized in autogenerated reports. The software was tested using 60 Skyn data sets recorded during 30 alcohol drinking episodes and 30 nonalcohol drinking episodes. Participants (N = 36; 13 with alcohol use disorder) wore the Skyn during one alcohol drinking episode and one nonalcohol drinking episode in their natural environment. In terms of distinguishing alcohol from nonalcohol drinking, correcting artifacts in the data resulted in 10% improvement in model accuracy relative to using raw data. Random forest and logistic regression models were both accurate, correctly predicting 97% (58/60; AUC-ROCs = 0.98, 0.96) of episodes. Area under TAC curve, rise duration of TAC curve, and peak TAC were the most important features for predictive accuracy. With promising model performance, this protocol will enhance the efficiency and reliability of TAC sensors for future alcohol monitoring research. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

College Students' Day-to-Day Maladaptive Drinking Responses to Stress Severity and Stressor-Related Guilt and Anger

BACKGROUND

Stress is a common part of college students' daily lives that may influence their physical activity (PA) and alcohol use. Understanding features of daily stress processes that predict health behaviors could help identify targets for just-in-time interventions.

PURPOSE

This study used intensive longitudinal data to examine whether prior day stress processes predict current day PA or alcohol use.

METHODS

Participants (N=58, Mage=20.5, 59% women, 70% White) were 18-to-25-year-old students who engaged in binge drinking at least twice monthly and used cannabis or tobacco in the past year. They wore activity (activPAL4) and alcohol (Secure Continuous Remote Alcohol Monitor) monitors for 11 days to assess daily PA (e.g., step counts) and alcohol use (e.g., drinking day), and completed daily surveys about yesterday's stress, including number of stressors (i.e., frequency), stressor intensity (i.e., severity), and frequency of affective states (e.g., guilt). Multilevel models examined prior day stress predicting current day PA or alcohol use.

RESULTS

Participants had higher odds of current day drinking (odds ratio=1.21) and greater area under the curve (B=0.08) when they experienced greater than usual stress severity the prior day. Participants had higher current day peak transdermal alcohol concentration (B=0.12) and area under the curve (B=0.11) when they more frequently experienced guilt due to stressors the prior day.

CONCLUSIONS

College students' unhealthy response of increasing alcohol use due to stress could adversely impact health outcomes. There is a critical need for interventions addressing students' ability to effectively manage and respond to the stress-inducing, daily demands of student life.

Accuracy of transdermal alcohol monitoring devices in a laboratory setting

The development of transdermal alcohol sensors (TASs) presents a new method to monitor alcohol consumption with the ability to objectively measure data 24/7. We aimed to evaluate the accuracy of two TASs (BACtrack Skyn and Smart Start BARE) in a laboratory setting. Thirty-two adults received a dose of ethanol 0.56 g/kg body weight as a 20% solution while wearing the two TASs and provided Breath Alcohol Concentration (BrAC) measurements for 3.5 h postalcohol consumption. Pearson's correlations and repeated measures analysis of variance tests were conducted on the peak, time-to-peak, and area under the curve data. Bland-Altman plots were derived. A time series analysis and cross-correlations were conducted to adjust for time lag. Both TASs were able to detect alcohol and increase within 20 min. BrAC peaked significantly quicker than Skyn and BARE. BrAC and Skyn peaks were negatively significantly correlated (r = -0.381, P = .035, n = 31), while Skyn and BARE peaks were positively significantly correlated (r = 0.380, P = .038, n = 30). Repeated measures analysis of variance found a significant difference between BrAC, Skyn, and BARE (F(1.946, 852.301) = 459.873, P < .001)). A time series analysis found when BrAC-Skyn and BrAC-BARE were adjusted for the delay to peak, and there was still a significant difference. Failure rates: 1.7% (Skyn) and 4.8% (BARE). Some evidence was obtained for TAS validity as both consistently detected alcohol. Failure rates and time lag show improvements in older device generations. However, neither TAS presented strong equivalence to the breathalyser even when the lag time was adjusted. With further testing and technology advancements, TAS could be a potential alcohol monitoring tool. Two of the newest TAS devices were worn in laboratory conditions for one afternoon to compare their accuracy of alcohol monitoring to a breathalyser. Findings suggest that the two TASs (BACtrack Skyn and SmartStart BARE) recorded significantly similar data postalcohol consumption, but not with the breathalyser.

Moderate alcohol consumption on the risk of stroke in the Million Veteran Program

BACKGROUND

There is inconsistent evidence on the association of moderate alcohol consumption and stroke risk in the general population and is not well studied among U.S. Veterans. Furthermore, it is unclear whether primarily drinking beer, wine, or liquor is associated with a difference in stroke risk.

METHODS

The study included 185,323 Million Veteran Program participants who self-reported alcohol consumption on the Lifestyle Survey. Moderate consumption was defined as 1-2 drinks/day and beverage preference of beer, wine or liquor was defined if ≥ 50% of total drinks consumed were from a single type of beverage. Strokes were defined using ICD-9 and ICD-10 codes from the participants' electronic health record.

RESULTS

The mean (sd) age of the sample was 64 (13) years and 11% were women. We observed 4,339 (94% ischemic; 6% hemorrhagic) strokes over a median follow-up of 5.2 years. In Cox models adjusted for age, sex, race, education, income, body mass index, smoking, exercise, diet, cholesterol, prevalent diabetes, prevalent hypertension, lipid-lowering medication, antihypertensive medication, and diabetes medication, moderate alcohol consumption (1-2 drinks/day) was associated with a 22% lower risk of total stroke compared with never drinking [Hazards ratio (HR) 95% confidence interval (CI): 0.78 (0.67, 0.92)]. When stratifying by stroke type, we observed a similar protective association with moderate consumption and ischemic stroke [HR (95% CI): 0.76 (0.65, 0.90)], but a non-statistically significant higher risk of hemorrhagic stroke [HR (95% CI): 1.29 (0.64, 2.61)]. We did not observe a difference in ischemic or hemorrhagic stroke risk among those who preferred beer, liquor or wine vs. no beverage preference. When stratifying by prior number of hospital visits (≤ 15, 16-33, 34-64, ≥ 65) as a proxy for health status, we observed attenuation of the protective association with greater number of visits [HR (95% CI): 0.87 (0.63, 1.19) for ≥ 65 visits vs. 0.80 (0.59, 1.08) for ≤ 15 visits].

CONCLUSIONS

We observed a lower risk of ischemic stroke, but not hemorrhagic stroke with moderate alcohol consumption and did not observe substantial differences in risk by beverage preference among a sample of U.S. Veterans. Healthy user bias of moderate alcohol consumption may be driving some of the observed protective association.

Effectiveness of contingency management using transdermal alcohol monitoring to reduce heavy drinking among driving while intoxicated (DWI) arrestees: A randomized controlled trial

BACKGROUND

Driving while intoxicated (DWI) is a serious public health problem. However, treatment for DWI arrestees is not readily available. This study examines the effectiveness of a contingency management (CM) procedure using transdermal alcohol concentration (TAC) monitoring to reduce drinking among DWI arrestees.

METHOD

The study participants were 216 DWI arrestees under pretrial and included both Mandated participants undergoing court-ordered TAC monitoring and Non-Mandated participants wearing a study-provided TAC monitor. Participants were randomly assigned to either a CM (Mandated = 35; Non-Mandated = 74) or a Control condition (Mandated = 37; Non-Mandated = 70) and completed the 8-week intervention. CM participants received $50/week for not exceeding a TAC of 0.02 g/dL during the previous week. Payments to Controls were yoked to the CM group.

RESULTS

Among Non-Mandated participants, the probability of meeting the contingency was higher and remained stable (about 65%) over time in the CM group, whereas the probability was lower and declined in the Control group, widening the gaps in the probability between the study conditions (16.7%-24.1% greater in the CM group from visit 4 to 8, all p < 0.05). Among Mandated participants, the probability was not significantly different between conditions (p = 0.06-0.95). Furthermore, among Non-Mandated participants, the percentage of heavy drinking days remained low (9.16%-11.37%) in the CM group, whereas it was greater and increased over time (17.43%-26.59%) in the Control group. In Mandated participants, no significant differences in percent heavy drinking days were observed between conditions (p = 0.07-0.10).

CONCLUSION

We found that contingency effects on alcohol use are more pronounced among frequent and heavy alcohol users, i.e., Non-Mandated DWI arrestees. However, for individuals whose drinking was already suppressed by existing contingencies (i.e., court-mandated TAC monitoring), our CM procedure did not produce additional reductions in drinking.

Wearable alcohol monitors for alcohol use data collection among college students: Feasibility and acceptability

OBJECTIVE

We assessed the feasibility and acceptability of using BACtrack Skyn wearable alcohol monitors for alcohol research in a college student population.

METHODS

We enrolled n = 5 (Sample 1) and n = 84 (Sample 2) Indiana University undergraduate students to wear BACtrack Skyn devices continuously over a 5-day to 7-day study period. We assessed feasibility in both samples by calculating compliance with study procedures, and by analyzing amount and distributions of device output [e.g., transdermal alcohol content (TAC), temperature, motion]. In Sample 1, we assessed feasibility and acceptability with the Feasibility of Intervention Measure (FIM) scale and the Acceptability of Intervention Measure (AIM) scale.

RESULTS

All participants were able to successfully use the alcohol monitors, producing a total of 11,504 h of TAC data. TAC data were produced on 567 days of the 602 total possible days of data collection. The distribution of the TAC data showed between-person variation, as would be expected with between-person differences in drinking patterns. Temperature and motion data were also produced as expected. Sample 1 participants (n = 5) reported high feasibility and acceptability of the wearable alcohol monitors in survey responses with a mean FIM score of 4.3 (of 5.0 possible score) and mean AIM score of 4.3 (of 5.0 possible score).

CONCLUSIONS

The high feasibility and acceptability we observed underscore the promise of using BACtrack Skyn wearable alcohol monitors to improve our understanding of alcohol consumption among college students, a population at particularly high risk for alcohol-related harms.

Acceptability and anklet user experience with the SCRAM-CAM transdermal alcohol concentration sensor in regularly drinking young adults' natural environments

Recent developments in wearable technologies have allowed for device-based capture of alcohol concentration among participants in their natural environments. Currently, the Continuous Alcohol Monitor from SCRAM systems (SCRAM-CAM) is the most extensively studied and validated transdermal alcohol concentration (TAC) sensor. However, there has been relatively little work focusing on its acceptability from the participants' perspective. In the current study, we assess the user experience of the SCRAM-CAM anklet in a sample of 222 regularly heavy drinking young adults (mean age = 22.3) who wore the anklet in their natural environments for five 24-h periods spanning 6 consecutive days. Differences in the anklet user experience were measured along a number of dimensions, and differences were tested by sex at birth, white/non-white racial/ethnic group membership, and alcohol use disorder (AUD) risk (measured through Alcohol Use Disorder Identification Test [AUDIT] scores). Males and females differed significantly on six of the eight acceptability items, with males showing more positive responses toward the anklet than females. No differences were found by white/non-white racial/ethnic groups nor AUD risk. Results suggest positive levels of acceptability toward the device overall while in natural environments, further validating the usage of the device in studies that measure alcohol consumption among different groups, including those with high levels of alcohol consumption. Researchers should take into consideration the different levels of burden or discomfort in male versus female participants when using the device.

Use of the BACtrack Skyn alcohol biosensor: Practical applications for data collection and analysis

AIMS

Alcohol biosensors, including the BACtrack Skyn, provide an objective and passive method of continuously assessing alcohol consumption in the natural environment. Despite the many strengths of the Skyn, six key challenges in the collection and processing of data include (1) identifying consumed alcohol; (2) identifying environmental alcohol; (3) identifying and determining the source of missing or invalid data; (4) achieving high participant adherence; (5) integrating Skyn and self-report data; and (6) implications for statistical inference. In this report we outline these challenges, provide recommendations to address them and identify future needs.

DESIGN AND SETTINGS

Procedures from several laboratory and field-based pilot studies are presented to demonstrate practical recommendations for Skyn use. Data from a pilot study including a 7-day ecological momentary assessment period are also presented to evaluate effects of environmental alcohol on BACtrack Skyn readings.

CONCLUSIONS

To address challenges in the collection and processing of data from the BACtrack Skyn alcohol biosensor, researchers should identify goals in advance of data collection to anticipate the processing necessary to interpret Skyn data. The Transdermal Alcohol Sensor Data Macro (TASMAC) version 2.0 software can help to process data rapidly; identify drinking events, missing data and environmental alcohol; and integrate the sensor with self-report data. Thorough participant orientation and regular contact in field studies can reduce missing data and enhance adherence. Many recommended methods for Skyn use are applicable to other alcohol sensors and wearable devices.

Acceptability and validity of using the BACtrack skyn wrist-worn transdermal alcohol concentration sensor to capture alcohol use across 28 days under naturalistic conditions - A pilot study

Wrist-worn transdermal alcohol concentration (TAC) sensors have the potential to provide detailed information about day-level features of alcohol use but have rarely been used in field-based research or in early adulthood (i.e., 26-40 years) alcohol users. This pilot study assessed the acceptability, user burden, and validity of using the BACtrack Skyn across 28 days in individuals' natural settings. Adults aged 26-37 (N = 11, Mage = 31.2, 55% female, 73% non-Hispanic white) participated in a study including retrospective surveys, a 28-day field protocol wearing Skyn and SCRAM sensors and completing ecological momentary assessments (EMA) of alcohol use and duration (daily morning reports and participant-initiated start/stop drinking EMAs), and follow-up interviews. Day-level features of alcohol use extracted from self-reports and/or sensors included drinks consumed, estimated Blood Alcohol Concentration (eBAC), drinking duration, peak TAC, area under the curve (AUC), rise rate, and fall rate. Repeated-measures correlations (rrm) tested within-person associations between day-level features of alcohol use from the Skyn versus self-report or the SCRAM. Participants preferred wearing the Skyn over the SCRAM [t (10) = -6.79, p < .001, d = 2.74]. Skyn data were available for 5614 (74.2%) out of 7566 h, with 20.7% of data lost due to syncing/charging issues and 5.1% lost due to device removal. Skyn agreement for detecting drinking days was 55.5% and 70.3% when compared to self-report and the SCRAM, respectively. Correlations for drinking intensity between self-report and the Skyn were 0.35 for peak TAC, 0.52 for AUC, and 0.30 for eBAC, which were smaller than correlations between self-report and SCRAM, at 0.78 for peak TAC, 0.79 for AUC, and 0.61 for eBAC. Correlations for drinking duration were larger when comparing self-report to the Skyn (rrm = 0.36) versus comparing self-report to the SCRAM (rrm = 0.31). The Skyn showed moderate-to-large, significant correlations with the SCRAM for peak TAC (rrm = 0.54), AUC (rrm = 0.80), and drinking duration (rrm = 0.63). Our findings support the acceptability and validity of using the Skyn for assessing alcohol use across an extended time frame (i.e., 28 days) in individuals' natural settings, and for providing useful information about day-level features of alcohol use.

Correspondence between alcohol use measured by a wrist-worn alcohol biosensor and self-report via ecological momentary assessment over a 2-week period

BACKGROUND

Transdermal alcohol biosensors measure alcohol use continuously, passively, and non-invasively. There is little field research on the Skyn biosensor, a new-generation, wrist-worn transdermal alcohol biosensor, and little evaluation of its sensitivity and specificity and the day-level correspondence between transdermal alcohol concentration (TAC) and number of self-reported drinks.

METHODS

Participants (N = 36; 61% male, M age  = 34.3) wore the Skyn biosensor and completed ecological momentary assessment (EMA) surveys about their alcohol use over 2 weeks. A total of 497 days of biosensor and EMA data were collected. Skyn-measured drinking episodes were defined by TAC > 5 μg/L. Skyn data were compared to self-reported drinking to calculate sensitivity and specificity (for drinking day vs. nondrinking day). Generalized estimating equations models were used to evaluate the correspondence between TAC features (peak TAC and TAC-area under the curve (AUC)) and number of drinks. Individual-level factors (sex, age, race/ethnicity, body mass index, human immunodeficiency virus status, and hazardous drinking) were examined to explore associations with TAC controlling for number of drinks.

RESULTS

Using a minimum TAC threshold of 5 μg/L plus coder review, the biosensor had sensitivity of 54.7% and specificity of 94.6% for distinguishing drinking from nondrinking days. Without coder review, the sensitivity was 78.1% and the specificity was 55.2%. Peak TAC (β = 0.92, p < 0.0001) and TAC-AUC (β = 1.60, p < 0.0001) were significantly associated with number of drinks. Females had significantly higher TAC levels than males for the same number of drinks.

CONCLUSIONS

Skyn-derived TAC can be used to measure alcohol use under naturalistic drinking conditions, additional research is needed to accurately identify drinking episodes based on Skyn TAC readings.

To Drink or Not to Drink: Is That the Question? Examining Correspondence and Predictive Validity of Morning Drinking Intentions for Young Adults' Drinking Behaviors and Consequences

The Theory of Planned Behavior suggests that intentions are significant and proximal determinants of behavior. The purpose of this study was to test the predictive validity of drinking intentions for subsequent same-day drinking behaviors and negative consequences. Regularly drinking young adults (N = 222, 21-29 years, 84% undergraduates) completed an ecological momentary assessment (EMA) protocol and wore an alcohol monitor for five consecutive 24-h periods spanning 6 days (Wednesday-Monday). Each morning, participants reported their drinking intentions for the day and their previous day's alcohol consumption and the number of negative drinking consequences. Multilevel models showed that, at the within-person level, on days when people reported intending to drink, to get drunk, or to drink more than usual, they had higher odds of drinking, consumed more drinks, and had higher peak transdermal alcohol concentrations later that day. However, drinking occurred on 28% of days without drinking intentions, suggesting intentions were an imperfect signal for future drinking behavior. Morning drinking intentions also predicted experiencing more negative consequences, even after controlling for alcohol consumption. On average, young adults' morning-reported drinking-related intentions predicted increased odds of same-day drinking behavior and alcohol-related consequences. However, drinking frequently occurred on days participants did not intend to drink, suggesting that focusing only on drinking intention days will result in many missed prevention opportunities. Together, these results suggest the need for additional research to increase the predictive value of drinking intention assessments and for prevention interventions aimed at helping individuals follow through on their intentions not to drink.

Reduced alcohol use increases drink-refusal self-efficacy: Evidence from a contingency management study for DWI arrestees

BACKGROUND

Several therapies and interventions to reduce drinking first target drink-refusal self-efficacy (DRSE) to influence drinking behavior. While higher self-efficacy scores are correlated with better outcomes, it is unclear that increased self-efficacy is the causative step leading to improved outcomes. Instead, this correlation may result from reduced drinking that increased self-efficacy. The current study sought to understand how changes in drinking behavior can influence DRSE.

METHODS

Data were from 211 driving while intoxicated (DWI) arrestees participating in an 8-week contingency management (CM) study to reduce drinking. Some of participants were mandated by the courts to wear transdermal alcohol monitoring devices (Mandated group) and some were not mandated (Non Mandated group). All wore a transdermal alcohol monitor during the 8-week study and were randomized to CM or a Control condition stratified by the mandate group. Participants completed weekly assessments of DRSE. Group-based trajectory-modeling identified three drinking behavior trajectory groups.

RESULTS

While there were no differences in baseline DRSE between the three trajectory groups, participants in the low- and moderate-frequency drinking behavior groups significantly increased DRSE across the study.

CONCLUSION

The present study indicates that being able to maintain abstinence or reduce heavy drinking may increase DRSE.

Sensitivity, specificity, and tolerability of the BACTrack Skyn compared to other alcohol monitoring approaches among young adults in a field-based setting

BACKGROUND

There is a need for novel alcohol biosensors that are accurate, able to detect alcohol concentration close in time to consumption, and feasible and acceptable for many clinical and research applications. We evaluated the field accuracy and tolerability of novel (BACTrack Skyn) and established (Alcohol Monitoring Systems SCRAM CAM) alcohol biosensors.

METHODS

The sensor and diary data were collected in a larger study of a biofeedback intervention and compared observationally in the present sub-study. Participants (high-risk drinkers, 40% female; median age 21) wore both Skyn and SCRAM CAM sensors for 1-6 days and were instructed to drink as usual. Data from the first cohort of participants (N = 27; 101 person-days) were used to find threshold values of transdermal alcohol that classified each day as meeting or not meeting defined levels of drinking (heavy, above-moderate, any). These values were used to develop scoring metrics that were subsequently tested using the second cohort (N = 20; 57 person-days). Data from both biosensors were compared to mobile diary self-report to evaluate sensitivity and specificity in relation to a priori standards established in the literature.

RESULTS

Skyn classification rules for Cohort #1 within 3 months of device shipment showed excellent sensitivity for heavy drinking (94%) and exceeded expectations for above-moderate and any drinking (78% and 69%, respectively), while specificity met expectations (91%). However, classification worsened when Cohort #1 devices ≥3 months from shipment were tested (area under curve for receiver operator characteristic 0.87 vs. 0.79) and the derived classification threshold when applied to Cohort #2 was inadequately specific (70%). Skyn tolerability metrics were excellent and exceeded the SCRAM CAM (p ≤ 0.001).

CONCLUSIONS

Skyn tolerability was favorable and accuracy rules were internally derivable but did not yield useful scoring metrics going forward across device lots and months of usage.

Accuracy of Wearable Transdermal Alcohol Sensors: Systematic Review

BACKGROUND

There are a range of wearable transdermal alcohol sensors that are available and are being developed. These devices have the potential to monitor alcohol consumption continuously over extended periods in an objective manner, overcoming some of the limitations of other alcohol measurement methods (blood, breath, and urine).

OBJECTIVE

The objective of our systematic review was to assess wearable transdermal alcohol sensor accuracy.

METHODS

A systematic search of the CINAHL, Embase, Google Scholar, MEDLINE, PsycINFO, PubMed, and Scopus bibliographic databases was conducted in February 2021. In total, 2 team members (EB and SH) independently screened studies for inclusion, extracted data, and assessed the risk of bias. The methodological quality of each study was appraised using the Mixed Methods Appraisal Tool. The primary outcome was transdermal alcohol sensor accuracy. The data were presented as a narrative synthesis.

RESULTS

We identified and analyzed 32 studies. Study designs included laboratory, ambulatory, and mixed designs, as well as randomized controlled trials; the length of time for which the device was worn ranged from days to weeks; and the analyzed sample sizes ranged from 1 to 250. The results for transdermal alcohol concentration data from various transdermal alcohol sensors were generally found to positively correlate with breath alcohol concentration, blood alcohol concentration, and self-report (moderate to large correlations). However, there were some discrepancies between study reports; for example, WrisTAS sensitivity ranged from 24% to 85.6%, and specificity ranged from 67.5% to 92.94%. Higher malfunctions were reported with the BACtrack prototype (16%-38%) and WrisTAS (8%) than with SCRAM (2%); however, the former devices also reported a reduced time lag for peak transdermal alcohol concentration values when compared with SCRAM. It was also found that many companies were developing new models of wearable transdermal alcohol sensors.

CONCLUSIONS

As shown, there is a lack of consistency in the studies on wearable transdermal alcohol sensor accuracy regarding study procedures and analyses of findings, thus making it difficult to draw direct comparisons between them. This needs to be considered in future research, and there needs to be an increase in studies directly comparing different transdermal alcohol sensors. There is also a lack of research investigating the accuracy of transdermal alcohol sensors as a tool for monitoring alcohol consumption in clinical populations and use over extended periods. Although there is some preliminary evidence suggesting the accuracy of these devices, this needs to be further investigated in clinical populations.

TRIAL REGISTRATION

PROSPERO CRD42021231027; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=231027.

Preliminary Effectiveness of a Remotely Monitored Blood Alcohol Concentration Device as Treatment Modality: Protocol for a Randomized Controlled Trial

Background

Alcohol use disorder is a chronic disorder with a high likelihood of relapse. The consistent monitoring of blood alcohol concentration through breathalyzers is critical to identifying relapse or misuse. Smartphone apps as a replacement of or in conjunction with breathalyzers have shown limited effectiveness. Yet, there has been little research that has effectively utilized wireless or Wi-Fi–enabled breathalyzers that can accurately, securely, and reliably measure blood alcohol concentration.

Objective

The purpose of this study is to evaluate the impact of a wireless blood alcohol concentration device in collaboration with long-term treatment on dropout rates, psychological distress, treatment motivation, quality of life, and need for higher levels of follow-up care for patients with alcohol use disorder.

Methods

The randomized clinical trial will include two arms, access to the wireless breathalyzer versus no access to the breathalyzer, while both groups have access to treatment. Evaluation will last 3 months with a 6-week follow-up, during which each participant will be interviewed at admission, 1 month in, 2 months in, 3 months in, and follow-up. Individuals will be recruited online through a secure telehealth meeting invitation. Outcomes will focus on the impact of the wireless breathalyzer within the alcohol use disorder population, and the combined effect on psychological distress, treatment motivation, and quality of life. In addition, we intend to investigate the impact of the breathalyzer on dropout rates and participants’ need for higher levels of follow-up care and treatment.

Results

The recruitment of this study started in July 2020 and will run until 2022.

Conclusions

This information will be important to develop cost-effective treatments for alcohol dependence. Ongoing monitoring allows treatment providers to take an individualized disease management approach and facilitates timely intervention by the treatment provider.

Trial Registration

ClinicalTrials.gov NCT04380116; http://clinicaltrials.gov/ct2/show/NCT04380116

International Registered Report Identifier (IRRID)

DERR1-10.2196/30186

Transdermal sensor features correlate with ecological momentary assessment drinking reports and predict alcohol-related consequences in young adults' natural settings

BACKGROUND

Wearable transdermal alcohol concentration (TAC) sensors allow passive monitoring of alcohol concentration in natural settings and measurement of multiple features from drinking episodes, including peak intoxication level, speed of intoxication (absorption rate) and elimination, and duration. These passively collected features extend commonly used self-reported drink counts and may facilitate the prediction of alcohol-related consequences in natural settings, aiding risk stratification and prevention efforts.

METHOD

A total of 222 young adults aged 21-29 (M age = 22.3, 64% female, 79% non-Hispanic white, 84% undergraduates) who regularly drink heavily participated in a 5-day study that included the ecological momentary assessment (EMA) of alcohol consumption (daily morning reports and participant-initiated episodic EMA sequences) and the wearing of TAC sensors (SCRAM-CAM anklets). The analytic sample contained 218 participants and 1274 days (including 554 self-reported drinking days). Five features-area under the curve (AUC), peak TAC, rise rate (rate of absorption), fall rate (rate of elimination), and duration-were extracted from TAC-positive trajectories for each drinking day. Day- and person-level associations of TAC features with drink counts (morning and episodic EMA) and alcohol-related consequences were tested using multilevel modeling.

RESULTS

TAC features were strongly associated with morning drink reports (r = 0.6-0.7) but only moderately associated with episodic EMA drink counts (r = 0.3-0.5) at both day and person levels. Higher peaks, larger AUCs, faster rise rates, and faster fall rates were significantly predictive of day-level alcohol-related consequences after adjusting for both morning and episodic EMA drink counts in separate models. Person means of TAC features added little above daily scores to the prediction of alcohol-related consequences.

CONCLUSIONS

These results support the utility of TAC sensors in studies of alcohol misuse among young adults in natural settings and outline the specific TAC features that contribute to the day-level prediction of alcohol-related consequences. TAC sensors provide a passive option for obtaining valid and unique information predictive of drinking risk in natural settings.

Daily Physical Activity, Sedentary Behavior and Alcohol Use in At-Risk College Students

BACKGROUND

The college years present an opportunity to establish health behavior patterns that can track across adulthood. Health behaviors tend to cluster synergistically however, physical activity and alcohol have shown a positive association.

PURPOSE

This study applied a multi-method approach to estimate between- and within-person associations between daily physical activity, sedentary behavior and alcohol use among polysubstance-using college students.

METHODS

Participants were screened for recent binge drinking and either tobacco or cannabis use. They wore an activPAL4 activity monitor and a Secure Continuous Remote Alcohol Monitor continuously in the field for 11 days, and completed daily online questionnaires at the beginning of each day to report previous day physical activity, sedentary behavior, and alcohol consumption.

RESULTS

Participants (N = 58, Mage = 20.5 years, 59% women, 69% White) reported meeting national aerobic physical activity guidelines (75%) and drinking 2-4 times in the past month (72%). On days when participants reported an hour more than usual of daily sedentary behavior, they reported drinking for less time than usual (γ = -.06). On days when participants took 1,000 more steps than usual, the longest episode of continuous transdermal alcohol detection was shorter (γ = -.03).

CONCLUSIONS

Daily physical activity and sedentary behavior were negatively associated with time-based measures of alcohol use with the lowest risk on days characterized by both activity and sedentary behavior. Intensive longitudinal monitoring of time-based processes can provide new insights into risk in multiple behavior change and should be prioritized for future work.

Wrist-worn alcohol biosensors: Applications and usability in behavioral research

Wrist-worn alcohol biosensor technology has developed rapidly in recent years. These devices are light, easy to wear, relatively inexpensive, and resemble commercial fitness trackers. As a result, they may be more suitable for a wide range of clinical and research applications. In this paper, we describe three pilot projects examining the associations between reported drinking behavior and transdermal alcohol concentration (TAC) derived from a new, wrist-worn alcohol biosensor (BACtrack Skyn) in diverse participant groups and settings. Study 1 (N = 3) compared Skyn-derived TAC with that from an ankle-worn alcohol sensor (SCRAM CAM) and breath alcohol concentration (BrAC) in a laboratory setting. Study 2 (N = 10) compared Skyn TAC with BrAC during a naturalistic drinking episode in the field. Study 3 (N = 12) used the Skyn to monitor alcohol use in the field for 2 weeks. Studies 2 and 3 also collected usability and acceptability data from participants. The results of Study 1 showed that the Skyn produced a TAC curve that closely resembled that of the validated SCRAM CAM anklet. In Study 2, Skyn detected drinking for all 10 participants (peak BrAC range: 0.02-0.21) with an average delay of 35.6 ± 10.2 min after the start of self-reported drinking. In Study 3, Skyn reliably recorded continuous TAC data showing multiple drinking episodes over the monitoring period. Participants in Studies 2 and 3 both reported Skyn as highly acceptable. Collectively, the results of these pilot studies show that the Skyn was able to reliably detect drinking events in the laboratory and natural environments. We offer suggestions for further refinements of alcohol biosensors and accompanying analytic software that may facilitate adoption of these devices as cost-effective, user-friendly, and reliable tools to passively and accurately assess alcohol use in the field.

Ecological Momentary Assessment of Alcohol Consumption and Its Concordance with Transdermal Alcohol Detection and Timeline Follow-Back Self-report Among Adults Experiencing Homelessness

Background

Studies of alcohol use presume valid assessment measures. To evaluate this presumption, we examined the concordance of alcohol use as measured by ecological momentary assessment (EMA) self‐reports, transdermal alcohol concentration readings via the Secure Continuous Remote Alcohol Monitor (SCRAM), and retrospective self‐reports via the Timeline Follow‐Back (TLFB) among adults experiencing homelessness.

Methods

Forty‐nine adults who reported alcohol misuse (mean age = 47, SD = 9; 57% Black; 82% men) were recruited from a homeless shelter. For 4 weeks, alcohol use was assessed: (i) 5 times or more per day by EMA, (ii) every 30 minutes by a SCRAM device worn on the ankle, and (iii) by TLFB for the past month at the end of the study period. There were 1,389 days of observations of alcohol use and alcohol use intensity for 49 participants.

Results

EMA and SCRAM alcohol use data agreed on 73% of days, with an interrater agreement Kappa = 0.46. A multilevel analysis of concordance of 3 measures for alcohol use yielded statistically significant correlations of 0.40 (day level) and 0.63 (person level) between EMA and SCRAM. Alcohol use was detected on 49, 38, and 33% of days by EMA, SCRAM, and TLFB, respectively. For alcohol use intensity, EMA and SCRAM resulted in statistically significant correlations of 0.46 (day level) and 0.78 (person level). The concordance of TLFB with either EMA or SCRAM was weak, especially at the day level.

Conclusions

This is the first study to examine concordance of alcohol use estimates using EMA, SCRAM, and TLFB methods in adults experiencing homelessness. EMA is a valid approach to quantifying alcohol use, especially given its relatively low cost, low participant burden, and ease of use. Furthermore, any stigma associated with wearing the SCRAM or reporting alcohol use in person may be attenuated by using EMA, which may be appealing for use in studies of stigmatized and underserved populations.

A Discreet Wearable IoT Sensor for Continuous Transdermal Alcohol Monitoring - Challenges and Opportunities

Non-invasive continuous alcohol (ethanol) monitoring has potential applications in both population research and in clinical management of acute alcohol intoxication or chronic alcoholism. Current wearable monitors based on transdermal alcohol content (TAC) sensing have limited accessibility and blood alcohol content (BAC) quantification accuracy. Here we describe the development of a self-contained discreet wearable transdermal alcohol (TAC) sensor in the form of a wristband or armband. This sensor can detect vapor-phase alcohol in perspiration from 0.09 ppm (equivalent to 0.09 mg/dL sweat alcohol concentration at 25 °C under Henry's Law equilibrium) to over 500 ppm at one-minute time resolution. Additionally, a digital sensor was employed to monitor the temperature and humidity levels inside the sensing chamber. Two male human subjects were recruited to conduct studies with alcohol consumption using calibrated prototype TAC sensors to validate the performance. Our preliminary data demonstrated that, under well-controlled conditions, this sensor can acquire TAC curves at low doses (1-2 standard drinks). Moreover, TAC data for different doses can be easily distinguished. However, substantial interpersonal and intrapersonal variabilities in measurement data were also observed in experiments with less controlled conditions. Our observations suggest that perspiration rate might be an important contributing factor to these variabilities. Further studies with sufficient sample sizes are required to validate and characterize the impact of different perspiration rates on TAC sensors, which may inform more reproducible and accurate sensor designs in the future.

Validation of transdermal alcohol concentration data collected using wearable alcohol monitors: A systematic review and meta-analysis

OBJECTIVE

To evaluate the diagnostic accuracy of transdermal alcohol content (TAC) data (i.e. index test) collected with wearable alcohol monitors for assessment of alcohol use or any other alcohol related outcome (e.g., excessive alcohol use) among adults 18 and older.

METHODS

We will systematically search MEDLINE, EMBASE, PsycINFO, and the Social Sciences Citation Index (SSCI, Web of Science) for TAC validation studies. The reference standards for this systematic review study are alcohol use data collected through self-reports, breathalyzers, or blood samples. If enough studies are available to conduct a meta-analysis, we will use a hierarchical regression approach to pool the results and obtain summary point estimates.

Outcome Assessment in Trials of Pharmacological Treatments for Alcohol Use Disorders: Fair and Strict Testing

Outcome assessment in the pharmacological treatment of alcohol use disorders (AUDs) faces specific challenges resulting from low adherence to treatment, high rates of dropout, and the susceptibility of patient self-reports to bias. This review discusses methodological issues in planning, conducting, and interpreting clinical trials on AUD treatment against the background of the principle of 'strictness and fairness' of testing. Threats to fairness include factors that limit the implementation of an intervention, such as low compliance and early treatment termination. In turn, fairness of testing is increased by factors that support the degree to which an intervention is implemented, such as the use of adequate pretreatments and the matching of psychosocial and pharmacological treatment strategies. Furthermore, selecting outcomes on the basis of an intervention's mechanism of action and including continuous outcomes as sensitive measures of drinking change further increases fairness by increasing the likelihood that the data will adequately reflect the effects of the intervention. On the other hand, strictness of testing is increased by all measures that limit the influence of confounders that could potentially lead to an overestimation of effects. The use of a side effect-mimicking placebo to prevent an unmasking of blinding and the repeated assessment of alcohol biomarkers to validate drinking self-reports might be valid strategies to further increase the strictness of testing by limiting risks of bias in trials of AUD treatment.

Assessment of Alcohol Use in the Natural Environment

The current article critically reviews 3 methodological options for assessing drinking episodes in the natural environment. Ecological momentary assessment (EMA) typically involves using mobile devices to collect self-report data from participants in daily life. This technique is now widely used in alcohol research, but investigators have implemented diverse assessment strategies. This article focuses on "high-resolution" EMA protocols that oversample experiences and behaviors within individual drinking episodes. A number of approaches have been used to accomplish this, including using signaled follow-ups tied to drinking initiation, asking participants to log entries before and after individual drinks or drinking episodes, and delivering frequent signaled assessments during periods of the day when alcohol use is most common. Transdermal alcohol sensors (TAS) are devices that are worn continuously and are capable of detecting alcohol eliminated through the skin. These methods are appealing because they do not rely upon drinkers' self-report. Studies using TAS have been appearing with greater frequency over the past several years. New methods are making the use of TAS more tractable by permitting back-translation of transdermal alcohol concentration data to more familiar estimates of blood alcohol concentration or breath alcohol concentration. However, the current generation of devices can have problems with missing data and tend to be relatively insensitive to low-level drinking. An emerging area of research investigates the possibility of using mobile device data and machine learning to passively detect the user's drinking, with promising early findings. EMA, TAS, and sensor-based approaches are all valid, and tend to produce convergent information when used in conjunction with one another. Each has a unique profile of advantages, disadvantages, and threats to validity. Therefore, the nature of the underlying research question must dictate the method(s) investigators select.